Printed circuit boards ("PCBs") normally have many electronic components soldered to their conducing surfaces. Such devices can include surface mounted and leaded-through-hole components, such as a dual-inline-package ("DIP") or a pin grid array ("PGA"), which are carefully placed by machine or hand into the plated-through-holes or onto surface mount pads of the PCB and are then typically wave or reflow soldered in place.
As is often the case with large scale soldering techniques, flowing solder wets the surface mount pads or through the plated-through-holes of the PCB and tends to creep or "wick" up the lead of the component. Wicking, as it is known in the art, is undesirable because it can lead to component damage, lead socket inoperability, shorting and poor solder efficiency.
In an effort to overcome the wicking problem, PCB manufacturers have in the past employed strips of anti-wicking material or mechanical interruptions in connection with the lead assembly to minimize undesired solder flow. See Hanlon, U.S. Pat. No. 3,989,331 ("'331"); and Senor et al., U.S. Pat. No. 4,723,923 ("'923"), which are hereby incorporated by reference.
Hanlon '331 discloses a dual-in-line package socket assembly having a bend or "dap" in its elongated contact lead for providing an interference fit between a lead and its corresponding PCB hole. The dap also provides a mechanical interruption of solder wicking so that continued upward flow of solder during wave soldering is disrupted.
Hanlon's socket can additionally include a polyester wafer mounted directly to the underside of the assembly so as to substantially cover the cavity between the socket contact fingers to prevent solder build up. The wafer has slots which are dimensioned to closely approximate the cross-section of the leads of the contacts to thereby hold the wafer in place and prevent solder from flowing up the lead into the space between the contact fingers.
Alternatively, Hanlon '331 teaches that a solder barrier strip, such as a Teflon.RTM. resin, epoxy or metal oxide can be applied to the surface of the contact lead to prevent wetting of the solder, and thus, wicking.
Senor et al. '923 provides an electrical lead socket assembly formed from a composite stamped fabrication. The lead of this assembly includes a strip of anti-wicking material, such as aluminum, which is applied to the composite prior to stamping. This anti-wicking strip deters solder bridging between the socket and the lower portion of its lead.
Although prior art solder barriers, wafers and anti-wicking strips have been adequate in overcoming the wicking problem in certain instances, these solutions require intricate and costly process steps for coating the lead assembly which are a burden to manufacturers in an already far too competitive market.